1. Field of the Invention
The invention is directed to an improved a fuel injection system for an internal combustion engine.
2. Description of the Prior Art
One fuel injection system of the type with which this invention is concerned is known from the literature, such as Dieselmotor-Management [Diesel Engine Management], published by Verlag Vieweg, 2nd Edition, 1998, page 262. This fuel injection system has a prefeed pump, through which fuel from a fuel supply container is pumped to a high-pressure pump. By the high-pressure pump, fuel is pumped into a reservoir, communicating with which are injectors through which fuel is injected into the engine. Between the prefeed pump and the high-pressure pump is a fuel filter. A return line for uninjected fuel from the injectors is provided, which discharges into the fuel supply container and thus into a region upstream of the high-pressure pump. A disadvantage of this is that a high fuel quantity must constantly be aspirated by the prefeed pump, yet some of this has to be returned to the fuel supply container again. The prefeed pump must therefore be made correspondingly large.
The fuel injection system of the invention has the advantage over the prior art that because of the return of uninjected fuel by the prefeed pump to between the prefeed pump and the high-pressure pump, a smaller fuel quantity has to be pumped, and so the pump can be made correspondingly smaller. The valve moreover makes it possible for the returned fuel to be introduced selectively upstream or downstream of the fuel filter.
Other advantageous features and refinements of the fuel injection system of the invention are disclosed. By means of one embodiment, damage to the fuel filter from severe heating can be averted. Another embodiment makes rapid heating of the fuel filter possible, which particularly at low ambient temperatures prevents the fuel filter from becoming clogged with congealed fuel. The valve can furthermore be controlled as a function of engine operating parameters.